The present invention relates in general to a sewing machine and, more particularly, to an improved device for lubricating a sewing machine looptaker.
A looptaker lubricating device is disclosed in West German Pat. No. 22 50 015 of the type having a looper arranged above a workpiece in a swivel arm and a cloth-clamping frame which moves in dependence on the movement of the swivel arm. The looptaker lubricating device has a capillary means, arranged in an oil line that has one end which dips into the oil of an oil storage vessel and another end which is movably mounted on the housing of the sewing machine. When the cloth-clamping frame is lifted, the moving end of the capillary means is swivelled in an exposed area of the bearing fin of the bobbin cage and feeds a small amount of oil to the bearing fin.
The fact that the capillary means is only pressed on the bearing fin of the bobbin case when the sewing machine stands still assures, on the one hand, a sufficient oil supply to the looper, and on the other hand, avoids an excess supply of oil during the operation of the sewing machine. Since the cloth-clamping frame is raised when the sewing machine is turned off, the capillary means during the entire stationary period bears on the bearing fin of the bobbin case. Since the capillary means connects the oil storage vessel with the bearing fin of the bobbin cage, the capillary means constantly draw some oil off from the storage vessel and delivers it to the bearing fin. During extended standstill periods, therefore, the bobbin cage, and thus the looptaker, can be flooded with oil.
In a looptaker device disclosed in U.S. Pat. No. 2,417,403, the looptaker of a sewing machine is lubricated with an oil mist through the hollow looper shaft. The lubricating device contains an injector nozzle with a mixing chamber which has two inlets and one outlet opening into the hollow looper shaft. One inlet of the mixing chamber is connected to a compressed air source which can be turned on and off by means of a manually operated valve. The other inlet is connected to a suction pipe into which the outlet of a drip oiler opens. The drip oiler has a valve with an adjustable flow cross-section that can be completely closed by means of a lever. The compressed air flowing through the injector nozzle produces a vacuum in the mixing chamber so that air and oil drops, dripping from the air oiler, are sucked in through the suction pipe. The oil drops are whirled by the compressed air to form an oil mist which flows through the hollow looper shaft in the looper and lubricates its bearing surfaces.
Since the oil supply can be completely isolated in this lubricating device by closing the oiler, the looptaker can thereby be prevented from being flooded with oil during longer standstill periods. This requires however, that an operator actually close the valve at the start of a longer standstill period. Otherwise the drip oiler will constantly drip, even with the sewing machine turned off, and the oil will eventually fill the suction pipe, the mixing chamber and the hollow looptaker shaft, leading to flooding of the looper when the machine is again turned on. Since compressed air flows constantly in a running sewing machine through the injector nozzle, and thus through the looptaker, the tendency to cast off small oil droplets which exist anyway in rapidly rotating loopers due to the centrifugal force, is increased further. Therefore, there is a risk that the sewing machine and the sewing material will be soiled by cast-off oil droplets.